Page 150 - Six Sigma Demystified

Chapter 6 a n a ly z e S tag e 131

Figure­6.5 Contingency table of errors by product (using Minitab).

lated to confirmations of receipt or status inquiries.) a large number of potential
sources was listed, and then the team used the nominal group technique (dis-
cussed in Part 3) to quickly reach consensus on the following areas for further
investigation:
• Product family
• Person entering order
• Number of line items in order
• Call volume (time of day/day of week)
• Number of available staff

These potential factors will be evaluated in the next section.

Determining­Process­Drivers

Designed experiments are a critical part of many successful improvement proj-
ects. While SPC provides a view of the past performance of the process, de-
signed experiments provide a view of the process potential. They allow an
understanding of the sources of the common and special causes of variation
seen on the control chart or the variation between subsets of a population.
In a designed experiment, each of the factors suspected of being significant
is varied, several at a time over a wide range, and the process responses are